The work being proposed deals with the continuing characterization of yeast nuclear and mitochondrial nucleic acids and of yeast RNA polymerases. The nuclear and cytoplasmic studies will deal with the location of ribosomal cistrons on various linkage groups using velocity sedimentation of intact chromosomal DNA followed by DNA-ribosomal RNA hybridization; the cytoplasmic work will deal with the characterization of the several yeast DNA-dependent RNA polymerases, of poly A polymerase, as well as with the isolation of mutants that affect these enzymes. Also, an attempt will be made to duplicate specific transcription in vitro of the various RNA species by the RNA polymerases, using fractionated yeast nuclear DNA as templates. The research plans dealing with mitochondria involve: the isolation of nuclear and of conditional lethal mitochondrial mutants affecting mitochondrial biogenesis, the characterization of yeast mitochondrial DNA of wild type and petite strains and the characterization of mitochondrial gene products using a coupled transcription-translation system starting with purified yeast mitochondrial DNA. The RNA polymerase used in the coupled system will be isolated from E. coli as well as from cytoplasm and/or yeast mitochondria.